Increased tractor horsepower has resulted in larger implements capable of planting or working a much wider swath in a single pass. Transport of these wide implements from a storage area to a field or from one field to another over roads has become an important design consideration. Some early planters required separate trailers for transport. In addition to the cost of these special-use transport trailers, these planters are limited in length by the practical requirements of having to load the implement on the trailer and to unload it. The time involved with the use of a separate trailer is increased because in loading the implement on the trailer and then in setting up the implement in the new field, the tractor must be unhitched from the implement and then hitched to the trailer, with the reverse procedure followed at the new site. This loss of time can be significant in view of the short time typically available when good planting conditions prevail, particularly when numerous fields must be planted using the same implement.
Other attempts to facilitate transport of larger implements include frames with pivoting wing sections on which row units are mounted which may be vertically folded. When folded, the implement is much greater in height, frequently causing problems when attempting to pass under bridges, through gates and into storage buildings. In addition, even with the two outer wing sections folded, because of the increasing size of agricultural implements, the fixed center section may also restrict transport and storage of the implement.
One improvement in planter design is disclosed in my U.S. Pat. No. 4,117,893. This design allows the planter bar to fold rearwardly about its centerline, with links used to lock the two side sections, or wings, either in the use position, wherein the mounting bars are aligned and transverse to the direction of travel, or in the transport position in which the mounting bars for the two sets of row units are folded rearwardly and are parallel to the direction of travel of the tractor. Another improvement in planter design is represented by the system disclosed in my U.S. Pat. No. 4,506,904. This system permits the planter bar to be transported end-wise rather than by folding. My U.S. Pat. No. 4,721,168 discloses another improvement in large implement transport and storage which employs a cylindrical vertical pivot post for rotating a lift frame in combination with four bar linkage for raising and lowering the lift frame on a carrier frame.